<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    .big-font{
      font-size: 50px;
    }
    .red{
      color: red;
    }
    .underline{
      text-decoration: underline;
    }
  </style>
</head>
<body>
    <p class="red big-font">段落1</p>
    <p class="red underline">段落2</p>
    <p class="underline big-font">段落3</p>
    <p class="underline big-font red">段落4</p>
</body>
</html>